The present invention relates to an opto-electronic A/D converter with a plurality of parallel-connected optical wave guide interferometers.
A known opto electronic 4-bit A/D converter of this type is constructed from four integrated optical Mach-Zehnder interferometers having electro optical phase modulators. The interferometers have a common input, to which a laser light source is connected. In this arrangement an interferometer is associated with each bit of the signal which is to be digitalised. The analog input signal is applied as an electrical voltage to the phase modulators, which have an electrode or contact length which decreases from the lowest bit (LSB) to the highest bit (MSB). The length is so dimensioned in each case that the four interference signals (light/dark conditions of the light intensity) registered from the photo diodes to the interferometer outputs represent the analog input voltage in the gray-code (Electronic Letters, Dec. 9, 1982, vol. VL 18 No. 25, pp. 1099-1100).
An electro optical multi-stable element is further known which relates to a conventional Fabry-Perot resonator with an electro optical crystal as the phase modulator between the mirrors. The length of the optical resonator is controlled by a voltage applied to the modulator via the electro optical effect. By feeding back the transmitted signal to the modulator this arrangement becomes multistable, i.e. a continuously changed input light power radiated into the resonator produces a stepwise changing discrete transmitted output signal. In the treatise quoted, 14 stable stages were produced (Optical Engineering 19 (4) (1980), p. 456).
Furthermore, tests are known on the bistable characteristics and multivibrator properties of an integrated optical Mach-Zehnder interferometer with feedback on to electro optical phase modulators (IEEE J. Quantum Electron. QE 18 (12) (1982), pp. 2010-2015.